Optical films for directing light towards active areas of displays

ABSTRACT

In various embodiments of the invention, an interferometric display device is provided having an external film with a plurality of structures that redirect light from an inactive area of the display to an active area of the display. Light incident on the external film that would normally continue towards an inactive area of the display is either reflected, refracted, or scattered towards an active area of the display comprising moveable and static reflective surfaces that form an optical cavity.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.11/156,162, filed Jun. 17, 2005, issued as U.S. Pat. No. 7,561,323 onJul. 14, 2009, which claims priority benefit under 35 U.S.C. §119(e) toU.S. Provisional Application Ser. No. 60/613,535, filed Sep. 27, 2004,each of which is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The field of the invention relates to microelectromechanical systems(MEMS).

2. Description of the Related Technology

Microelectromechanical systems (MEMS) include micro mechanical elements,actuators, and electronics. Micromechanical elements may be createdusing deposition, etching, and or other micromachining processes thatetch away parts of substrates and/or deposited material layers or thatadd layers to form electrical and electromechanical devices. One type ofMEMS device is called an interferometric modulator. As used herein, theterm interferometric modulator or interferometric light modulator refersto a device that selectively absorbs and/or reflects light using theprinciples of optical interference. In certain embodiments, aninterferometric modulator may comprise a pair of conductive plates, oneor both of which may be transparent and/or reflective in whole or partand capable of relative motion upon application of an appropriateelectrical signal. In a particular embodiment, one plate may comprise astationary layer deposited on a substrate and the other plate maycomprise a metallic membrane separated from the stationary layer by anair gap. As described herein in more detail, the position of one platein relation to another can change the optical interference of lightincident on the interferometric modulator. Such devices have a widerange of applications, and it would be beneficial in the art to utilizeand/or modify the characteristics of these types of devices so thattheir features can be exploited in improving existing products andcreating new products that have not yet been developed.

SUMMARY

The system, method, and devices of the invention each have severalaspects, no single one of which is solely responsible for its desirableattributes. Without limiting the scope of this invention, its moreprominent features will now be discussed briefly. After considering thisdiscussion, and particularly after reading the section entitled“Detailed Description of Certain Embodiments” one will understand howthe features of this invention provide advantages over other displaydevices.

In one embodiment, a display is provided, the display comprising: alight-modulating array comprising a plurality of light-modulatingelements, said light-modulating elements including movable reflectivesurfaces and static reflective surfaces that define active reflectorareas of the light-modulating array spaced apart by substantiallynon-reflective portions; and an optical layer above the light-modulatingarray, the optical layer including a plurality of optical elementsseparated by gaps, wherein the gaps between the optical elements areabove the active reflector areas and the optical elements are above thesubstantially non-reflective portions of the light modulating array, theoptical elements being configured to re-direct light incident thereoninto the active reflector areas of the light-modulating array.

In another embodiment, a method of manufacturing a display is provided,the method comprising: forming a light-modulating array comprising aplurality of light-modulating elements, said light-modulating elementsincluding movable reflective surfaces and static reflective surfacesthat define active reflector areas of the light-modulating array spacedapart by substantially non-reflective portions; and forming an opticallayer above the light-modulating array, the optical layer including aplurality of optical elements separated by gaps, wherein the gapsbetween the optical elements are above the active reflector areas andthe optical elements are above the substantially non-reflective portionsof the light modulating array, the optical elements being configured tore-direct light incident thereon into the active reflector areas of thelight-modulating array.

In another embodiment, a display is provided, the display comprising: alight-modulating array comprising a plurality of light-modulatingelements, said light-modulating elements including movable reflectivesurfaces and static reflective surfaces that define active reflectorareas of the light-modulating array spaced apart by non-reflectiveportions; and means for directing light into the active reflector areasof the light-modulating array.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric view depicting a portion of one embodiment of aninterferometric modulator display in which a movable reflective layer ofa first interferometric modulator is in a relaxed position and a movablereflective layer of a second interferometric modulator is in an actuatedposition.

FIG. 2 is a system block diagram illustrating one embodiment of anelectronic device incorporating a 3×3 interferometric modulator display.

FIG. 3 is a diagram of movable mirror position versus applied voltagefor one exemplary embodiment of an interferometric modulator of FIG. 1.

FIG. 4 is an illustration of a set of row and column voltages that maybe used to drive an interferometric modulator display.

FIGS. 5A and 5B illustrate one exemplary timing diagram for row andcolumn signals that may be used to write a frame of display data to the3×3 interferometric modulator display of FIG. 2.

FIGS. 6A and 6B are system block diagrams illustrating an embodiment ofa visual display device comprising a plurality of interferometricmodulators.

FIG. 7A is a cross section of the device of FIG. 1.

FIG. 7B is a cross section of an alternative embodiment of aninterferometric modulator.

FIG. 7C is a cross section of another alternative embodiment of aninterferometric modulator.

FIG. 7D is a cross section of yet another alternative embodiment of aninterferometric modulator.

FIG. 7E is a cross section of an additional alternative embodiment of aninterferometric modulator.

FIG. 8A is side view of a display device with an external film.

FIG. 8B is a side view of an interferometric modulator device configuredfor displaying information in RGB color.

FIG. 8C is a side view of an interferometric modulator device configuredfor displaying information in black and white.

FIG. 9 is a side view of an interferometric modulator device configuredwith a light diffuser on its outer surface.

FIG. 10 is a side view of an interferometric modulator device configuredwith a light diffuser on its outer surface, where the light diffuserincludes diffusing particles.

FIG. 11A is a side view of an interferometric modulator deviceconfigured with a grooved front light plate that is separated from theinterferometric modulator device by an air gap.

FIG. 11B is a side view of an interferometric modulator deviceconfigured with a grooved front light plate connected to theinterferometric modulator device.

FIG. 11C is a side view of an interferometric modulator deviceconfigured with an external film which has a contoured outer surface sothat light provided from a light source is redirected to theinterferometric modulator device and reflected out of theinterferometric modulator to a viewer.

FIG. 12A is a side view of an interferometric modulator deviceconfigured with an external film that includes baffle structures thatlimit the field-of-view of the interferometric modulator device.

FIG. 12B is a side view of one embodiment of an interferometricmodulator device showing how baffle structures contained in the externalfilm limit the direction of the reflected light.

FIGS. 12C and 12D are embodiments of an external film having bafflestructures comprising opaque columns.

FIGS. 12E-12G are embodiments of external films having baffle structurescomprising opaque portions.

FIG. 12H depicts an external film having baffle structures comprisingreflective material.

FIG. 13A is a side view of an interferometric modulator display thatincludes a touchscreen.

FIGS. 13B-D show different approaches for incorporating a diffusingmaterial.

FIG. 14A is a side view of an interferometric modulator deviceconfigured with a touchscreen comprising diffuser material that scatterslight from a light source toward the interferometric modulator device.

FIGS. 14B1 and 14B2 show different configurations for delivering lightfrom a light source to the interferometric modulators device.

FIGS. 14C-E demonstrate different approaches for integrating diffusingmaterial into displays for directing light from a light source to theinterferometric display device.

FIGS. 15A and 15B are side views of interferometric modulator devicesconfigured with a film that directs at least a portion of light incidenton the space between the active reflector areas to the active reflectorareas.

FIG. 16A is a side view of an external film having regions that scatterlight.

FIG. 16B is a side view of an external film having regions of higherrefractive index in a matrix of lower refractive indices material thatredirect light.

FIG. 16C is a side view of an external film having a surface havingdimpled regions that act as concave lenses.

FIG. 16D is a side view of an external film having a surface comprisingFresnel lenses.

FIG. 16E is a side view of an external film having opposing slopedsurfaces configured that refract light in opposite directions.

FIG. 16F is a side view of an external film having sloped surfacesconfigured to refract light toward one direction.

FIG. 16G is a side view of an external film having sloped surfacesconfigured to reflect light.

FIG. 17 is a side view of an interferometric modulator device configuredwith an external film that changes the direction of light that isincident on the external film, to provide the light to active reflectorareas of the interferometric modulator device at an angle that is moreperpendicular than its incident angle at the external film.

FIG. 18A is a side view of an interferometric modulator deviceconfigured with an external film comprising a diffusing elementconfigured to collimate light directed toward the interferometricmodulator device.

FIG. 18B is a side view of the interferometric modulator of FIG. 18Ashowing that the incident light is collimated and redirected to theactive reflector areas of the interferometric modulator device.

FIG. 18C is a side view of the interferometric modulator device of FIG.18A showing that light reflected from the active areas of theinterferometric modulator device is diffused by the external film.

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS OF THE INVENTION

Microelectromechanical systems (MEMS) include micro mechanical elements,actuators, and electronics. Micromechanical elements may be createdusing deposition, etching, and or other micromachining processes thatetch away parts of substrates and/or deposited material layers or thatadd layers to form electrical and electromechanical devices. One type ofMEMS device is called an interferometric modulator. As used herein, theterm interferometric modulator or interferometric light modulator refersto a device that selectively absorbs and/or reflects light using theprinciples of optical interference. In certain embodiments, aninterferometric modulator may comprise a pair of conductive plates, oneor both of which may be transparent and/or reflective in whole or partand capable of relative motion upon application of an appropriateelectrical signal. In a particular embodiment, one plate may comprise astationary layer deposited on a substrate and the other plate maycomprise a metallic membrane separated from the stationary layer by anair gap. As described herein in more detail, the position of one platein relation to another can change the optical interference of lightincident on the interferometric modulator. Such devices have a widerange of applications, and it would be beneficial in the art to utilizeand/or modify the characteristics of these types of devices so thattheir features can be exploited in improving existing products andcreating new products that have not yet been developed.

In various embodiments of the invention, an interferometric displaydevice is provided having an external film with a plurality ofstructures that redirect light from an inactive area of the display toan active area of the display. Light incident on the external film thatwould normally continue towards an inactive area of the display iseither reflected, refracted, or scattered towards an active area of thedisplay comprising a moveable and static reflective surfaces that forman optical cavity.

One interferometric modulator display embodiment comprising aninterferometric MEMS display element is illustrated in FIG. 1. In thesedevices, the pixels are in either a bright or dark state. In the bright(“on” or “open”) state, the display element reflects a large portion ofincident visible light to a user. When in the dark (“off” or “closed”)state, the display element reflects little incident visible light to theuser. Depending on the embodiment, the light reflectance properties ofthe “on” and “off” states may be reversed. MEMS pixels can be configuredto reflect predominantly at selected colors, allowing for a colordisplay in addition to black and white.

FIG. 1 is an isometric view depicting two adjacent pixels in a series ofpixels of a visual display, wherein each pixel comprises a MEMSinterferometric modulator. In some embodiments, an interferometricmodulator display comprises a row/column array of these interferometricmodulators. Each interferometric modulator includes a pair of reflectivelayers positioned at a variable and controllable distance from eachother to form a resonant optical cavity with at least one variabledimension. In one embodiment, one of the reflective layers may be movedbetween two positions. In the first position, referred to herein as therelaxed position, the movable reflective layer is positioned at arelatively large distance from a fixed partially reflective layer. Inthe second position, referred to herein as the actuated position, themovable reflective layer is positioned more closely adjacent to thepartially reflective layer. Incident light that reflects from the twolayers interferes constructively or destructively depending on theposition of the movable reflective layer, producing either an overallreflective or non-reflective state for each pixel.

The depicted portion of the pixel array in FIG. 1 includes two adjacentinterferometric modulators 12 a and 12 b. In the interferometricmodulator 12 a on the left, a movable reflective layer 14 a isillustrated in a relaxed position at a predetermined distance from anoptical stack 16 a, which includes a partially reflective layer. In theinterferometric modulator 12 b on the right, the movable reflectivelayer 14 b is illustrated in an actuated position adjacent to theoptical stack 16 b.

The optical stacks 16 a and 16 b (collectively referred to as opticalstack 16), as referenced herein, typically comprise of several fusedlayers, which can include an electrode layer, such as indium tin oxide(ITO), a partially reflective layer, such as chromium, and a transparentdielectric. The optical stack 16 is thus electrically conductive,partially transparent and partially reflective, and may be fabricated,for example, by depositing one or more of the above layers onto atransparent substrate 20. In some embodiments, the layers are patternedinto parallel strips, and may form row electrodes in a display device asdescribed further below. The movable reflective layers 14 a, 14 b may beformed as a series of parallel strips of a deposited metal layer orlayers (orthogonal to the row electrodes of 16 a, 16 b) deposited on topof posts 18 and an intervening sacrificial material deposited betweenthe posts 18. When the sacrificial material is etched away, the movablereflective layers 14 a, 14 b are separated from the optical stacks 16 a,16 b by a defined gap 19. A highly conductive and reflective materialsuch as aluminum may be used for the reflective layers 14, and thesestrips may form column electrodes in a display device.

With no applied voltage, the cavity 19 remains between the movablereflective layer 14 a and optical stack 16 a, with the movablereflective layer 14 a in a mechanically relaxed state, as illustrated bythe pixel 12 a in FIG. 1. However, when a potential difference isapplied to a selected row and column, the capacitor formed at theintersection of the row and column electrodes at the corresponding pixelbecomes charged, and electrostatic forces pull the electrodes together.If the voltage is high enough, the movable reflective layer 14 isdeformed and is forced against the optical stack 16. A dielectric layer(not illustrated in this Figure) within the optical stack 16 may preventshorting and control the separation distance between layers 14 and 16,as illustrated by pixel 12 b on the right in FIG. 1. The behavior is thesame regardless of the polarity of the applied potential difference. Inthis way, row/column actuation that can control the reflective vs.non-reflective pixel states is analogous in many ways to that used inconventional LCD and other display technologies.

FIGS. 2 through 5 illustrate one exemplary process and system for usingan array of interferometric modulators in a display application.

FIG. 2 is a system block diagram illustrating one embodiment of anelectronic device that may incorporate aspects of the invention. In theexemplary embodiment, the electronic device includes a processor 21which may be any general purpose single- or multi-chip microprocessorsuch as an ARM, Pentium®, Pentium II®, Pentium III®, Pentium IV®,Pentium® Pro, an 8051, a MIPS®, a Power PC®, an ALPHA®, or any specialpurpose microprocessor such as a digital signal processor,microcontroller, or a programmable gate array. As is conventional in theart, the processor 21 may be configured to execute one or more softwaremodules. In addition to executing an operating system, the processor maybe configured to execute one or more software applications, including aweb browser, a telephone application, an email program, or any othersoftware application.

In one embodiment, the processor 21 is also configured to communicatewith an array driver 22. In one embodiment, the array driver 22 includesa row driver circuit 24 and a column driver circuit 26 that providesignals to a display array or panel 30. The cross section of the arrayillustrated in FIG. 1 is shown by the lines 1-1 in FIG. 2. For MEMSinterferometric modulators, the row/column actuation protocol may takeadvantage of a hysteresis property of these devices illustrated in FIG.3. It may require, for example, a 10 volt potential difference to causea movable layer to deform from the relaxed state to the actuated state.However, when the voltage is reduced from that value, the movable layermaintains its state as the voltage drops back below 10 volts. In theexemplary embodiment of FIG. 3, the movable layer does not relaxcompletely until the voltage drops below 2 volts. There is thus a rangeof voltage, about 3 to 7 V in the example illustrated in FIG. 3, wherethere exists a window of applied voltage within which the device isstable in either the relaxed or actuated state. This is referred toherein as the “hysteresis window” or “stability window.” For a displayarray having the hysteresis characteristics of FIG. 3, the row/columnactuation protocol can be designed such that during row strobing, pixelsin the strobed row that are to be actuated are exposed to a voltagedifference of about 10 volts, and pixels that are to be relaxed areexposed to a voltage difference of close to zero volts. After thestrobe, the pixels are exposed to a steady state voltage difference ofabout 5 volts such that they remain in whatever state the row strobe putthem in. After being written, each pixel sees a potential differencewithin the “stability window” of 3-7 volts in this example. This featuremakes the pixel design illustrated in FIG. 1 stable under the sameapplied voltage conditions in either an actuated or relaxed pre-existingstate. Since each pixel of the interferometric modulator, whether in theactuated or relaxed state, is essentially a capacitor formed by thefixed and moving reflective layers, this stable state can be held at avoltage within the hysteresis window with almost no power dissipation.Essentially no current flows into the pixel if the applied potential isfixed.

In typical applications, a display frame may be created by asserting theset of column electrodes in accordance with the desired set of actuatedpixels in the first row. A row pulse is then applied to the row 1electrode, actuating the pixels corresponding to the asserted columnlines. The asserted set of column electrodes is then changed tocorrespond to the desired set of actuated pixels in the second row. Apulse is then applied to the row 2 electrode, actuating the appropriatepixels in row 2 in accordance with the asserted column electrodes. Therow 1 pixels are unaffected by the row 2 pulse, and remain in the statethey were set to during the row 1 pulse. This may be repeated for theentire series of rows in a sequential fashion to produce the frame.Generally, the frames are refreshed and/or updated with new display databy continually repeating this process at some desired number of framesper second. A wide variety of protocols for driving row and columnelectrodes of pixel arrays to produce display frames are also well knownand may be used in conjunction with the present invention.

FIGS. 4 and 5 illustrate one possible actuation protocol for creating adisplay frame on the 3×3 array of FIG. 2. FIG. 4 illustrates a possibleset of column and row voltage levels that may be used for pixelsexhibiting the hysteresis curves of FIG. 3. In the FIG. 4 embodiment,actuating a pixel involves setting the appropriate column to −V_(bias),and the appropriate row to +ΔV, which may correspond to −5 volts and +5volts respectively Relaxing the pixel is accomplished by setting theappropriate column to +V_(bias), and the appropriate row to the same+ΔV, producing a zero volt potential difference across the pixel. Inthose rows where the row voltage is held at zero volts, the pixels arestable in whatever state they were originally in, regardless of whetherthe column is at +V_(bias), or −V_(bias). As is also illustrated in FIG.4, it will be appreciated that voltages of opposite polarity than thosedescribed above can be used, e.g., actuating a pixel can involve settingthe appropriate column to +V_(bias), and the appropriate row to −ΔV. Inthis embodiment, releasing the pixel is accomplished by setting theappropriate column to −V_(bias), and the appropriate row to the same−ΔV, producing a zero volt potential difference across the pixel. As isalso illustrated in FIG. 4, it will be appreciated that voltages ofopposite polarity than those described above can be used, e.g.,actuating a pixel can involve setting the appropriate column to+V_(bias), and the appropriate row to −ΔV. In this embodiment, releasingthe pixel is accomplished by setting the appropriate column to−V_(bias), and the appropriate row to the same −ΔV, producing a zerovolt potential difference across the pixel.

FIG. 5B is a timing diagram showing a series of row and column signalsapplied to the 3×3 array of FIG. 2 which will result in the displayarrangement illustrated in FIG. 5A, where actuated pixels arenon-reflective. Prior to writing the frame illustrated in FIG. 5A, thepixels can be in any state, and in this example, all the rows are at 0volts, and all the columns are at +5 volts. With these applied voltages,all pixels are stable in their existing actuated or relaxed states.

In the FIG. 5A frame, pixels (1,1), (1,2), (2,2), (3,2) and (3,3) areactuated. To accomplish this, during a “line time” for row 1, columns 1and 2 are set to −5 volts, and column 3 is set to +5 volts. This doesnot change the state of any pixels, because all the pixels remain in the3-7 volt stability window. Row 1 is then strobed with a pulse that goesfrom 0, up to 5 volts, and back to zero. This actuates the (1,1) and(1,2) pixels and relaxes the (1,3) pixel. No other pixels in the arrayare affected. To set row 2 as desired, column 2 is set to −5 volts, andcolumns 1 and 3 are set to +5 volts. The same strobe applied to row 2will then actuate pixel (2,2) and relax pixels (2,1) and (2,3). Again,no other pixels of the array are affected. Row 3 is similarly set bysetting columns 2 and 3 to −5 volts, and column 1 to +5 volts. The row 3strobe sets the row 3 pixels as shown in FIG. 5A. After writing theframe, the row potentials are zero, and the column potentials can remainat either +5 or −5 volts, and the display is then stable in thearrangement of FIG. 5A. It will be appreciated that the same procedurecan be employed for arrays of dozens or hundreds of rows and columns. Itwill also be appreciated that the timing, sequence, and levels ofvoltages used to perform row and column actuation can be varied widelywithin the general principles outlined above, and the above example isexemplary only, and any actuation voltage method can be used with thesystems and methods described herein.

FIGS. 6A and 6B are system block diagrams illustrating an embodiment ofa display device 40. The display device 40 can be, for example, acellular or mobile telephone. However, the same components of displaydevice 40 or slight variations thereof are also illustrative of varioustypes of display devices such as televisions and portable media players.

The display device 40 includes a housing 41, a display 30, an antenna43, a speaker 44, an input device 48, and a microphone 46. The housing41 is generally formed from any of a variety of manufacturing processesas are well known to those of skill in the art, including injectionmolding, and vacuum forming. In addition, the housing 41 may be madefrom any of a variety of materials, including but not limited toplastic, metal, glass, rubber, and ceramic, or a combination thereof. Inone embodiment the housing 41 includes removable portions (not shown)that may be interchanged with other removable portions of differentcolor, or containing different logos, pictures, or symbols.

The display 30 of exemplary display device 40 may be any of a variety ofdisplays, including a bi-stable display, as described herein. In otherembodiments, the display 30 includes a flat-panel display, such asplasma, EL, OLED, STN LCD, or TFT LCD as described above, or anon-flat-panel display, such as a CRT or other tube device, as is wellknown to those of skill in the art. However, for purposes of describingthe present embodiment, the display 30 includes an interferometricmodulator display, as described herein.

The components of one embodiment of exemplary display device 40 areschematically illustrated in FIG. 6B. The illustrated exemplary displaydevice 40 includes a housing 41 and can include additional components atleast partially enclosed therein. For example, in one embodiment, theexemplary display device 40 includes a network interface 27 thatincludes an antenna 43 which is coupled to a transceiver 47. Thetransceiver 47 is connected to a processor 21, which is connected toconditioning hardware 52. The conditioning hardware 52 may be configuredto condition a signal (e.g. filter a signal). The conditioning hardware52 is connected to a speaker 45 and a microphone 46. The processor 21 isalso connected to an input device 48 and a driver controller 29. Thedriver controller 29 is coupled to a frame buffer 28, and to an arraydriver 22, which in turn is coupled to a display array 30. A powersupply 50 provides power to all components as required by the particularexemplary display device 40 design.

The network interface 27 includes the antenna 43 and the transceiver 47so that the exemplary display device 40 can communicate with one or moredevices over a network. In one embodiment the network interface 27 mayalso have some processing capabilities to relieve requirements of theprocessor 21. The antenna 43 is any antenna known to those of skill inthe art for transmitting and receiving signals. In one embodiment, theantenna transmits and receives RF signals according to the IEEE 802.11standard, including IEEE 802.11(a), (b), or (g). In another embodiment,the antenna transmits and receives RF signals according to the BLUETOOTHstandard. In the case of a cellular telephone, the antenna is designedto receive CDMA, GSM, AMPS or other known signals that are used tocommunicate within a wireless cell phone network. The transceiver 47pre-processes the signals received from the antenna 43 so that they maybe received by and further manipulated by the processor 21. Thetransceiver 47 also processes signals received from the processor 21 sothat they may be transmitted from the exemplary display device 40 viathe antenna 43.

In an alternative embodiment, the transceiver 47 can be replaced by areceiver. In yet another alternative embodiment, network interface 27can be replaced by an image source, which can store or generate imagedata to be sent to the processor 21. For example, the image source canbe a digital video disc (DVD) or a hard-disc drive that contains imagedata, or a software module that generates image data.

Processor 21 generally controls the overall operation of the exemplarydisplay device 40. The processor 21 receives data, such as compressedimage data from the network interface 27 or an image source, andprocesses the data into raw image data or into a format that is readilyprocessed into raw image data. The processor 21 then sends the processeddata to the driver controller 29 or to frame buffer 28 for storage. Rawdata typically refers to the information that identifies the imagecharacteristics at each location within an image. For example, suchimage characteristics can include color, saturation, and gray-scalelevel.

In one embodiment, the processor 21 includes a microcontroller, CPU, orlogic unit to control operation of the exemplary display device 40.Conditioning hardware 52 generally includes amplifiers and filters fortransmitting signals to the speaker 45, and for receiving signals fromthe microphone 46. Conditioning hardware 52 may be discrete componentswithin the exemplary display device 40, or may be incorporated withinthe processor 21 or other components.

The driver controller 29 takes the raw image data generated by theprocessor 21 either directly from the processor 21 or from the framebuffer 28 and reformats the raw image data appropriately for high speedtransmission to the array driver 22. Specifically, the driver controller29 reformats the raw image data into a data flow having a raster-likeformat, such that it has a time order suitable for scanning across thedisplay array 30. Then the driver controller 29 sends the formattedinformation to the array driver 22. Although a driver controller 29,such as a LCD controller, is often associated with the system processor21 as a stand-alone Integrated Circuit (IC), such controllers may beimplemented in many ways. They may be embedded in the processor 21 ashardware, embedded in the processor 21 as software, or fully integratedin hardware with the array driver 22.

Typically, the array driver 22 receives the formatted information fromthe driver controller 29 and reformats the video data into a parallelset of waveforms that are applied many times per second to the hundredsand sometimes thousands of leads coming from the display's x-y matrix ofpixels.

In one embodiment, the driver controller 29, array driver 22, anddisplay array 30 are appropriate for any of the types of displaysdescribed herein. For example, in one embodiment, driver controller 29is a conventional display controller or a bi-stable display controller(e.g., an interferometric modulator controller). In another embodiment,array driver 22 is a conventional driver or a bi-stable display driver(e.g., an interferometric modulator display). In one embodiment, adriver controller 29 is integrated with the array driver 22. Such anembodiment is common in highly integrated systems such as cellularphones, watches, and other small area displays. In yet anotherembodiment, display array 30 is a typical display array or a bi-stabledisplay array (e.g., a display including an array of interferometricmodulators).

The input device 48 allows a user to control the operation of theexemplary display device 40. In one embodiment, input device 48 includesa keypad, such as a QWERTY keyboard or a telephone keypad, a button, aswitch, a touch-sensitive screen, a pressure- or heat-sensitivemembrane. In one embodiment, the microphone 46 is an input device forthe exemplary display device 40. When the microphone 46 is used to inputdata to the device, voice commands may be provided by a user forcontrolling operations of the exemplary display device 40.

Power supply 50 can include a variety of energy storage devices as arewell known in the art. For example, in one embodiment, power supply 50is a rechargeable battery, such as a nickel-cadmium battery or a lithiumion battery. In another embodiment, power supply 50 is a renewableenergy source, a capacitor, or a solar cell, including a plastic solarcell, and solar-cell paint. In another embodiment, power supply 50 isconfigured to receive power from a wall outlet.

In some implementations control programmability resides, as describedabove, in a driver controller which can be located in several places inthe electronic display system. In some cases control programmabilityresides in the array driver 22. Those of skill in the art will recognizethat the above-described optimization may be implemented in any numberof hardware and/or software components and in various configurations.

The details of the structure of interferometric modulators that operatein accordance with the principles set forth above may vary widely. Forexample, FIGS. 7A-7E illustrate five different embodiments of themovable reflective layer 14 and its supporting structures. FIG. 7A is across section of the embodiment of FIG. 1, where a strip of metalmaterial 14 is deposited on orthogonally extending supports 18. In FIG.7B, the moveable reflective layer 14 is attached to supports at thecorners only, on tethers 32. In FIG. 7C, the moveable reflective layer14 is suspended from a deformable layer 34, which may comprise aflexible metal. The deformable layer 34 connects, directly orindirectly, to the substrate 20 around the perimeter of the deformablelayer 34. These connections are herein referred to as support posts. Theembodiment illustrated in FIG. 7D has support post plugs 42 upon whichthe deformable layer 34 rests. The movable reflective layer 14 remainssuspended over the cavity, as in FIGS. 7A-7C, but the deformable layer34 does not form the support posts by filling holes between thedeformable layer 34 and the optical stack 16. Rather, the support postsare formed of a planarization material, which is used to form supportpost plugs 42. The embodiment illustrated in FIG. 7E is based on theembodiment shown in FIG. 7D, but may also be adapted to work with any ofthe embodiments illustrated in FIGS. 7A-7C as well as additionalembodiments not shown. In the embodiment shown in FIG. 7E, an extralayer of metal or other conductive material has been used to form a busstructure 44. This allows signal routing along the back of theinterferometric modulators, eliminating a number of electrodes that mayotherwise have had to be formed on the substrate 20.

In embodiments such as those shown in FIG. 7, the interferometricmodulators function as direct-view devices, in which images are viewedfrom the front side of the transparent substrate 20, the side oppositeto that upon which the modulator is arranged. In these embodiments, thereflective layer 14 optically shields the portions of theinterferometric modulator on the side of the reflective layer oppositethe substrate 20, including the deformable layer 34. This allows theshielded areas to be configured and operated upon without negativelyaffecting the image quality. Such shielding allows the bus structure 44in FIG. 7E, which provides the ability to separate the opticalproperties of the modulator from the electromechanical properties of themodulator, such as addressing and the movements that result from thataddressing. This separable modulator architecture allows the structuraldesign and materials used for the electromechanical aspects and theoptical aspects of the modulator to be selected and to functionindependently of each other. Moreover, the embodiments shown in FIGS.7C-7E have additional benefits deriving from the decoupling of theoptical properties of the reflective layer 14 from its mechanicalproperties, which are carried out by the deformable layer 34. Thisallows the structural design and materials used for the reflective layer14 to be optimized with respect to the optical properties, and thestructural design and materials used for the deformable layer 34 to beoptimized with respect to desired mechanical properties.

As described above, a picture element (pixel) from a direct-view displaymay comprise elements such as the one shown in FIGS. 7A-7E. In variousembodiments, these modulator elements with the mirror 14 in anundeflected state will be bright, or ‘ON.’ When the mirror 14 moves toits full design depth into the cavity toward the front surface of thecavity, the change in the cavity causes the resulting pixel to be ‘dark’or OFF. For color pixels, the ON state of the individual modulatingelements may be white, red, green, blue, or other colors depending uponthe modulator configuration and the display color scheme. In someembodiments using red/green/blue (RGB) pixels, for example, a singlecolor pixel comprises a number of modulator elements that createinterferometric blue light, a similar number of elements that createinterferometric red light, and a similar number that createinterferometric green light. By moving the mirrors according to displayinformation, the modulator can produce full color images.

Various embodiments, include improvements that can be made to aninterferometric modulator device using various optical films. Theoptical films include films that come on rolls or in sheets. The film isattached to or near the interferometric modulator, and positioned sothat light reflected from the interferometric modulator passes throughthe film as it propagates to a viewer. The optical films can alsoinclude coatings that are spread, sputtered or otherwise deposited on asurface of the interferometric modulator so that light reflected fromthe interferometric modulator passes through the film as it propagatesto a viewer.

The films are generally disposed on an external surface of theinterferometric modulator so that desirable optical characteristics canbe achieved without changing the interferometric modulator itself.“External” as used herein refers to a placement of the film outside ofthe fabricated interferometric modulator, e.g., on the outer surface ofthe substrate of an interferometric modulator, such that the externalfilm can be applied after fabricating the interferometric modulatordisplay. The external film may be disposed on or near the surface of theinterferometric modulator which first receives incident light, which isreferred to herein as the outer surface of the interferometricmodulator. This outer surface is also the surface that is positionedproximal to a person viewing the interferometric modulator. The externalfilm may be on the layers that form the interferometric modulator or maybe formed on one or more layers formed on the interferometric modulator.Although various embodiments are generally described herein as beingexternal to the interferometric modulator display, these types of filmscan also be fabricated inside the interferometric modulator in otherembodiments, and/or characteristics of the external films described canbe incorporated into the interferometric modulator, e.g., duringfabrication of the interferometric modulator, to achieve a similareffect.

As illustrated in FIG. 8A, one embodiment of a display 100A includes aspatial light modulator 105 and an external film 110 positioned on ornear the outer surface 115 of the spatial light modulator 105. Thespatial light modulator 105 is a representation of an interferometricmodulator device that may include, for example, a substrate, a conductorlayer, a partial reflector layer, a dielectric layer and movablereflectors (referred to also as mirrors) configured with a gap betweenthe movable mirrors and the dielectric. The spatial light modulator 105may be, but is not limited to, a full color, monochrome, or black andwhite interferometric modulator display device. The design and operationof interferometric modulators are described in detail, e.g., in U.S.Pat. Nos. 6,650,455; 5,835,255; 5,986,796; and 6,055,090, all of whichare incorporated herein by reference.

The external film 110 can be fabricated in a variety of ways, includingfor example, using fabrication techniques where the external film 110 ispoured, spun, deposited on or laminated to the display. In someembodiments, the external film 110 is a single film layer, while inother embodiments the external film 110 includes more than one filmlayer. If the external film 110 comprises more than one film layer, eachfilm layer can have different properties that affect one or morecharacteristics of light reflecting from the spatial light modulator 105and propagating through the external film 110. Each layer of amulti-layer external film 110 can be fabricated by the same filmfabrication technique or a different film fabrication technique, forexample, any single layer can, for example, be poured, spun, depositedon or laminated to an adjacent layer. Other orientations andconfigurations are also possible.

Referring to FIG. 8B, one embodiment of a display 100B has an externalfilm 110 above an outer surface 115 of an RGB spatial light modulator105B comprising color interferometric modulators. In this embodiment,the RGB spatial light modulator 105B comprises a substrate 120 above amultilayer 126 comprising, for example, a conductive layer (which is atleast partially transmissive), a partially reflecting layer, anddielectric layer, which in turn is above a set of reflectors (e.g.mirrors) that includes red 150, green 160, and blue 170 reflectors, eachwith a different gap width 175, 180, 190, respectively, that correspondto the colors red, green, and blue. In certain embodiments, thesubstrate 120 can be between the external film 110 and the reflectors150, 160, 170, as depicted in FIG. 8B. In other embodiments, thereflectors 150, 160, 170 can be between the external film 110 and thesubstrate 120.

In other embodiments, the external film may be disposed above themonochrome or black and white interferometric modulator. As illustratedby FIG. 8C, the monochrome or black and white spatial light modulator105C comprises a substrate 120 above a conductive layer, a partiallyreflective layer 124, a dielectric layer 125, which in turn is above aset of reflectors (e.g. mirrors) 130, 135, 140. The monochrome spatiallight modulator 105C can be fabricated to have reflectors 130, 135, 140configured with a single gap width 145 between the reflectors 130, 135,140 and the dielectric layer 125.

In certain embodiments, the external film can diffuse light reflectingfrom the interferometric modulator display. The light reflecting fromthe interferometric modulator display may be at least partially diffuseso that the display has an appearance similar to paper (e.g., thedisplay appears diffusely reflecting).

Referring to FIG. 9, a display 300 can include an external diffuse film305 positioned on the spatial light modulator 105. Light 320 incident onthe display 300 is specularly reflected by reflective spatial lightmodulator 105. As the specularly reflected light 307 propagates from thedisplay 300, diffuse film 305 changes the characteristics of thespecularly reflected light 307, which is transformed into diffuse light330. The diffuser 305 also diffuses light incident on theinterferometric modulators.

Diffuse film 305 can be fabricated from a number of materials, and caninclude one or more layers of diffuse material. The diffuser 305 mayinclude material with surface variation (e.g. corrugations androughness) or variation in material. This variation can refract orscatter light in different embodiments. A wide variety of diffusers 305are possible and not limited to those recited herein.

FIG. 10 illustrates an exemplary embodiment of a display 400 thatproduces diffuse reflected light. The display 400 includes an externalfilm 405 attached to a spatial light modulator 105. The external film405 includes material 410 comprising scattering features (e.g.,particles) that scatter the light 403 reflecting from the spatial lightmodulator 105 to change the character of the light 407 emitted from theinterferometric modulator device from specular to diffuse.

In some embodiments, the external diffuse film 305 includes a materialthat changes the spectral characteristics of the reflected light 403 anda material that changes the diffuse or specular characteristics of thereflected light. Such material can be included in a single layer of theexternal film 305, 405 (FIGS. 9 and 10). Alternatively, material thatchanges the spectral characteristics of the reflected light can beincorporated in one layer of the external film 305 and material thatchanges the diffuse or specular characteristics of reflected light canbe incorporated in a separate layer of external film. In one embodiment,the diffuse material can be included in an adhesive that is used betweenthe external film 305 and the spatial light modulator 105 (FIG. 9).

As mentioned above, some type of diffuser is useful on interferometricmodulator displays where it is desired that the display 300, 400 has theappearance of paper rather than the appearance of a mirror. Of course,in some embodiments it can be desirable for the appearance of thedisplay 300, 400 or a portion of the display to be highly reflective or“mirror-like,” and in these embodiments the display may have a diffusefilm 305, 405 covering all or only a portion of the interferometricdisplay device 305, 405. In some embodiments, an optically transmissivelayer is “frosted” in order to achieve the desired diffusion. Forexample, the outer surface of the display 105 (FIG. 9) can be frosted toprovide diffusion of the reflected light. If the surface is heavilyfrosted, the light will be diffused more than if the surface is lightlyfrosted. In some embodiments, the optically transmissive layer that isfrosted may comprise a glass or polymer layer.

In some embodiments, it can be advantageous to include a light source(referred to herein as a “front light”) to provide additional light tothe interferometric modulator, e.g., for viewing the interferometricmodulator in dark or low ambient lighting conditions. Referring to FIG.11A, one embodiment of a display 500A includes a light source 515positioned on the side of a front plate 505. This front plate 505comprises material substantially optically transmissive to light 507from the light source 515. The front plate 505 may comprise, forexample, glass or plastic in some embodiments. The front plate 505 hasoptical features (e.g., contours such as grooves) configured to disruptpropagation of light in the front plate and redirect the light towardthe interferometric modulator display device 105. An air gap 525separates the contoured/grooved front plate 505 from the spatial lightmodulator 105. Operationally, the light source 515 provides light 507into the front plate 505, where the light 520 reflects off the slantedsurface features 506 and travels towards the spatial light modulator105. For ambient light entering the display 500, the air gap 525 reducesthe perceived contrast of the display 500A because of the differences inthe index of refraction between the air in the air gap 525 and thematerials which are used to form the front plate 505 and the spatiallight modulator 105.

Referring to FIG. 11B, the display 500B provides for a more efficienttransmission of light to the spatial light modulator 105 because it doesnot have an air gap separating the front plate 505 and the display 105.Instead, the front plate 505 is attached to the spatial light modulator105. While the configuration of display 500B increases the transmissionof light to the spatial light modulator 105, attaching the two pieces isnot a good manufacturing practice because the front plate 505 and thespatial light modulator 105 are both relatively expensive pieces, and ifeither piece exhibits a failure during manufacturing both pieces arelost.

Referring now to FIG. 11C, display 500C illustrates how the problemsexperienced by the displays 500A, 500B of FIGS. 11A and 11B are overcomeusing an external film rather than a front plate. As shown in FIG. 11C,the display 500C includes a light source 515 positioned next an edge 531of spatial light modulator 105 to which is laminated an external film530, which has a surface 514 comprising optical features such ascontouring, e.g., grooves or slanted surface features, configured toredirect light toward the spatial light modulator 105. The light source515 may, for example, be disposed at an edge of a substrate supportingthe interferometric modulator device 105. The external film 530 isattached to the spatial light modulator 105 or laminated onto thespatial light modulator 105. An adhesive may be used. The external film530 is relatively inexpensive compared to the cost of a grooved frontglass plate 505 (FIGS. 11A, 11B), so if the display 105 fails it can bedisposed without a large additional loss. Operationally, the externalfilm 530 receives light 511 from the light source 515. As the lightpropagates through the spatial light modulator 105 (e.g., the substrateof the interferometric modulator device) and the external film 530, thelight 511 reflects off of an inner portion of the contoured/groovedsurfaces 514 and the reflected light 513 propagates through thesubstrate of the interferometric modulator device and reflects offmirror surfaces of the interferometric modulators.

Referring now to FIG. 12A, in other embodiments a display 600 maycomprise an external film 605 that is attached to the outer surface ofthe spatial light modulator 105, where the external film comprises aplurality of structures 603 that reduce or minimize the field-of-view ofthe display. In one embodiment, structures 603 are small verticallyaligned obstructions which can be formed in a grid and “sunk” ordiffused into the external film 605. In another embodiment, the materialof the external film 605 provides the vertically aligned structures 603.These structures 603 may be referred to as baffles. The baffles 603 maybe substantially opaque. The baffles 603 may be substantially absorbingor reflective.

FIG. 12B illustrates how light reflected in a substantiallynon-perpendicular direction 607 is substantially blocked from exitingthe external film 605 and how light 609 reflected in a substantiallyvertical direction is not substantially obstructed by the structures603. In the embodiment shown in FIGS. 12A and 12B, the field of view islimited depending on the shape (and orientation), size (e.g., length),and spacing of the baffle structures 603. For example, the baffles 603may have a size, shape, and spacing to provide a field-of-view no morethan about 20 degrees or no more than about 40 degrees as measured froma plane 610 normal to a front surface 606 of the display 600. Thefield-of-view may therefore be between about 20, 25, 30, 35 and 40degrees or less as measured from the normal. In one exemplaryembodiment, the baffles 603 provide the display 600 with a field-of-viewof about 30 degrees. As used herein, the term baffle includes but is notlimited to the structures 603 depicted in FIGS. 12A and 12B.

The baffle structures 603 may be constructed in accordance withembodiments depicted in FIGS. 12C and 12D. For example, a plurality ofsubstantially vertically aligned columnars features 612 may comprise atransmissive material in the shape of columns having a coating of opaquematerial on an outer surface 612 a of the column-shaped transmissivematerial. The columnar features 612 may be bundled together and aligned.The space between the vertically aligned columnars features 612 may befilled with a transmissive material such as polycarbonate, polyethyleneterephtalate (PET), acrylic, or polymethylmethacrylate (PMMA) that formsa matrix 613 for these vertically aligned columnars features 612. Thematrix 613 having the columnars features 612 disposed therein may be cutperpendicular across line A-A to produce a thin film. A top view of thesection cut to form the external film 605 is depicted in FIG. 12D. Inthis embodiment, the opaque outer surface 612 a of the columnarsfeatures 612 substantially block light exiting the external film 605 insubstantially non-vertical directions.

The baffle structures 603 may also be constructed in accordance withother embodiments such as described with reference to FIGS. 12E and 12F.In FIG. 12E, a multilayer structure 618 having a plurality of stackedlayers is constructed. The multilayer structure 618 has alternatinglayers of a substantially transmissive material 615 and layers 614 ofsubstantially opaque material. To fabricate this multilayer structure618, an optically transmissive layer 615 that may comprise a slightlydiffuse material is formed and an opaque layer 614 comprising of asubstantially opaque material is formed thereon. These steps can berepeated until a desired number of layers have been formed. Themultilayer structure 618 can then be cut perpendicular across line A-A.A top view of the section cut to form the external film 605 is depictedin FIG. 12F. The substantially opaque layers 614 form the baffles 603that substantially block light exiting the external film 605 in asubstantially non-vertical direction.

As depicted in FIG. 12G, the external film 605 comprises atwo-dimensional grid comprising horizontal opaque layers 616 andvertical opaque layers 617. This two-dimensional grid may be fabricatedusing a pair of sections cut from the multilayer structure 618 (FIG.12E) with one section disposed in front of the other such as depicted inFIG. 12F. One of the sections is oriented substantially perpendicularrelative to the other external film structure 605. Other orientationsand configurations are also possible.

In certain embodiments, the baffle structures 603 shown in FIGS. 12C-12Gmay comprise reflective material. For example, referring to FIG. 12H, ifa portion 625 of the baffle structures 603 nearest to the spatial lightmodulator 105 is substantially reflective, then light 620 reflected fromthe spatial light modulator 105 that is incident on the reflectiveportion 625 of the baffle will not pass through the external filmstructure 605, but will be reflected back to the spatial light modulator105. Alternatively, the outer surfaces 603 a and 603 b of the bafflestructures 603 may be made of a substantially reflective material, suchas a flash coating of substantially reflective material on the bafflestructures 603. In this embodiment, the bottom portion 625 of the bafflestructures 603 may also be flash coated with the substantiallyreflective material.

In some embodiments, an interferometric modulator can incorporate a userinput device that can also change a characteristic of light reflectedfrom the interferometric modulator. For example, the display 700 in FIG.13A includes a touchscreen 705 which is connected to the outer surfaceof spatial light modulator 105. The touchscreen 705 includes an outertouchscreen portion 715 that has an outer touch surface 730 configuredto receive touch signals from a user, and a touchscreen inner portion720 which is attached to the spatial light modulator 105. Thetouchscreen inner portion 720 and touchscreen outer portion 715 areseparated by a space 710 and held apart by spacers 717. For user input,the touchscreen 705 can operate in a manner well known in the art, e.g.,a user applies pressure to the touch surface 730 on the othertouchscreen portion 715, which makes contact with the touch screen innerportion 720 and activates a circuit which is configured to send a signalwhen activated. In addition to providing user input functionality, thetouchscreen 705 can be configured with a light diffusing material 731 inthe touchscreen inner portion 720 and/or a light diffusing material 725in the touchscreen outer portion 715.

FIG. 13B is a side view of an embodiment of the touchscreen outerportion 715 and/or touchscreen inner portion 720 having a diffusingmaterial. In this embodiment, the diffusing material is a diffusingadhesive 751 between an upper layer 750 a and a lower layer 750 b. Thediffusing adhesive 751 may be an adhesive mixed with filler particles751 a that act as scatter centers for scattering light. Any suitablematerial that refracts, reflects, or scatters light may be used as thefiller particles 751 a. For example, the filler particles 751 a may bemade of materials such as, but not limited by, the following polymers:polystyrene silica, polymethyl-methacrylate (PMMA), and hollow polymerparticles. In an alternative embodiment the diffusing adhesive 751 isconfigured to have air bubbles that refract light. In other embodiments,opaque non-reflective particles may be used. The upper 750 a and/orlower 750 b layers may comprise materials such as polycarbonate,acrylic, and polyethylene terephtalate (PET) as well as other materials.FIG. 13C is another embodiment of the touchscreen outer portion 715and/or touchscreen inner portion 720 comprising a diffusing material,where diffusing material 752 is incorporated in a layer 750 that formsthe upper and/or lower portions 715, 720 of the touchscreen. FIG. 13D isan embodiment where diffusing material 753 is between the touchscreen705 and the spatial light modulator 105. For example, in FIG. 13D, thediffusing material 753 is coated on top of the outer surface 754 of thespatial light modulator 105. In this embodiment, the diffusing material753 may be patterned on the outer surface 754 of the display 105, wherethe diffusing material 753 is between the outer surface 754 of thespatial light modulator 105 and the touchscreen 705. In someembodiments, the diffusing material 753 may be spun, e.g., on a glassouter surface of the spatial light modulator 105. In certainembodiments, the diffusing material may comprise scatter features mixedwith an ultraviolet epoxy or thermally cured epoxy. When an epoxy isused, the diffusing material 753 may be filler particles mixed with theepoxy, where the filler particles act as scatter centers to scatterlight. Other configurations are also possible.

FIG. 14A shows an embodiment of a display 800 that includes atouchscreen 705 with an inner portion 720 attached to a spatial lightmodulator 105, which includes a substrate, and an outer portion 715 thathas a touchscreen surface 730 for receiving user input. Spacers 717 aredisposed in a gap 710 between the inner portion 720 and outer portion715. The display 800 also includes a light source 740 configured toprovide light 719 to the touchscreen 705, e.g., the inner portion 720,the outer portion 715, or both. In one embodiment, the touchscreen 705can include optical structures that redirect the light 719 so that thelight is incident on the spatial light modulator 105. In someembodiments, the optical structures comprise inclined or slantedsurfaces inside the touchscreen 705. In some embodiments, total internalreflection (TIR) elements may be used. Also, in certain embodiments, theoptical elements comprise particles that scatter light such that aportion of the scattered light is incident on the spatial lightmodulator 105. In some embodiments, the material 745 in the innerportion 720 and/or the material 735 in the outer portion 715 of thetouchscreen 705 can include phosphorescent material. This phosphorescentmaterial emits light when activated by the light 719 from the lightsource 740, providing light directly to the touchscreen 705 and to thespatial light modulator 105, which can then be reflected back to thetouchscreen 705.

In other embodiments depicted in FIGS. 14B1 and 14B2, the display 800with a touchscreen 705 may also include a contoured light guide. Forexample, in FIG. 14B1, the inner portion 720 of the touchscreen 705 maycomprise a plate or layer 760 a with a contoured, e.g., grooved, surface765. This contoured surface 765 may include a plurality of slantedportions. This surface 765 may have, for example, a sawtooth shape. Atransmissive material 760 b may then be placed in the contours orgrooves of the surface 765 to form a substantially planer surface 760 cabove the plate/layer 760 a. The light source 740 directs light 719 intothe plate or layer 760 a, where the light 719 is optically guided. Thelight propagating in the plate 760 a reflects off the slanted portion ofthe surface 765 and travels towards the spatial light modulator 105. Inthe embodiments using the light guiding plate or layer 760 a, or anyother suitable light guide, a diffuser material may be incorporated intothe display 800 above or below the plate 760 a. For example, thediffusing material may be within the outer portion 715 of thetouchscreen 705 or on the outer surface 754 of the spatial lightmodulator 105.

In an alternative embodiment depicted in FIG. 14B2, the plate or layer760 a may be placed between the touchscreen 705 and the spatial lightmodulator 105. In this embodiment, the transmissive material 760 b (FIG.14B1) is not placed on the surface 765 of the plate 760 a. Rather, airor vacuum occupies a cavity 760 c between the plate/layer 760 a and thetouchscreen 705.

In another embodiment illustrated in FIG. 14C, light 719 for the lightsource 740 may be directed into an edge of the touchscreen 705 and maybe guided through at least a portion of the touchscreen 705, and thetouchscreen 705 may comprise features that redirect this light towardthe spatial light modulator 105. For example, in FIG. 14C, the innerportion 720 of the touchscreen 705 may incorporate particles 770 thatscatter the light toward the spatial light modulator 105. As illustratedby FIG. 14D, the inner portion 720 may be a multi-layered with particles770 mixed in an adhesive between an upper layer 750 a and a lower layer750 b. The upper 750 a and/or lower 750 b layers may comprise materialssuch as polycarbonate, acrylic, and polyethylene terephtalate (PET), orother materials. In other embodiments such as depicted in FIG. 14E,scatter features or particles 770 are coated on top of the outer surface754 of the spatial light modulator 105. These scatter features orparticles 770 may redirect light toward the movable reflectors of theinterferometric modulators; see for example U.S. patent application Ser.No. 10/794,825, filed Mar. 5, 2004, and entitled “Integrated ModulatorIllumination”, issued as U.S. Pat. No. 7,706,050 on Apr. 27, 2010, whichis hereby incorporated by reference. In this embodiment, the scatterfeatures or particles 770 may be patterned on the outer surface 754 ofthe display 105, where the scatter features 770 are between the outersurface 754 of the spatial light modulator 105 and the touchscreen 705.In certain embodiments, the scatter features 770 may be spun on a glasssurface of the spatial light modulator 105. In some embodiments, scatterfeatures are mixed with an ultraviolet epoxy or thermally cured epoxy.When an epoxy is used, the scatter features 770 may comprise particlesmixed with the epoxy, where the particles act as scatter centers toredirect the light toward the mirrored surfaces of the interferometricmodulators.

FIG. 15A is a representation of one embodiment of a display 1100 thatuses the light incident on inactive areas between the active reflectorareas. As used herein, the term inactive area include but is not limitedto the space between the reflective areas (such as the mirrors) of aninterferometric modulator. As used herein, the active area includes butis not limited to the reflective areas (such as the mirrors) of aninterferometric modulator, for example, that form an optical cavity.

Referring to FIG. 15A, a display 1100 includes a film 1105 connected tothe outer surface of a spatial light modulator 105. Red 1121, green1122, and blue 1123 active reflector areas are shown on the bottom ofspatial light modulator 105 and represent the numerous active reflectorareas (e.g., resonant optical cavities) of the display 1100. A firstspace 1110 separates the red active reflector area 1121 from the greenactive reflector area 1122, which is separated from the blue activereflector area by a second space 1111. The spaces 1110 and 1111 may bebetween about 2 to 10 microns wide and are spaced apart from each otherby about 125 to 254 microns. Similarly, optical features in the spaces1110 and 1111 in the film 1105 that redirect light may be about 2 to 10microns wide and are spaced apart from each other by about 125 to 254microns. Dimensions outside these ranges are also possible.

Generally, without the film 1105, light incident on the areas of thefirst space 1110 or the second space 1111 may not reach one of theactive reflector areas 1121, 1122, 1123. To increase the reflectance ofthe interferometric modulator 1100, light incident on the inactive areasbetween the active reflector areas (e.g., first space 1110 and secondspace 1111) can be redirected to one of the active reflector areas 1121,1122, 1123. As the location of the inactive areas and the activereflector areas is known, the external film 1105 can be configured toredirect the light incident 1115 on the film 1105 in the inactive areas1110, 1111 back into the active reflector area 1121, 1122, 1123 (e.g.,the optical cavity) as shown by arrow 1120. In some embodiments, thefilm 1105 includes reflectors to re-direct the light. In someembodiments, the film 1105 is configured with a customized index ofrefraction in the areas of the spaces 1110, 1111 to re-direct the light.In other embodiments, the film 1105 can contain scattering elements inthe areas of the spaces 1110, 1111 so that at least a portion of thelight is scattered into and falls onto an active reflector area (e.g.,the optical cavity).

In an alternative embodiment depicted in FIG. 15B, the film 1105 may beplaced above reflector areas 1121, 1122, 1123 but below the substrate ofthe spatial light modulator 105. The film 1105 is, thus, in the spatiallight modulator 105. In this embodiment, the film 1105 is configured toredirect the light 1115, which is incident on an active area but wouldnormally proceed to an inactive area, to the active reflector areas1121, 1122, 1123 as shown by arrow 1120.

Referring to FIGS. 16A-H, various embodiments of the external film areillustrated. In FIG. 16A, external film 1205 has scatter regions 1212that scatter light. As depicted in FIG. 16A, these scatter regions 1212that scatter light may be interposed with regions 1217 that do notscatter light. The scatter regions 1212 may scatter light, for example,by reflection or refraction. Referring to FIG. 16B, external film 1205has regions of higher refractive index within a matrix or filmcomprising material of lower refractive index. This embodiment uses TIRto redirect light. For example, if the spaces of the external film 1205having a high refractive index are placed over the active regions of aninterferometric modulator and the spaces having a low refractive indexare placed over the inactive regions of the interferometric modulator,some of the light incident on the low refractive areas of the externalfilm 1205 that would normally pass through to the inactive areas will beredirected to the active areas of the interferometric modulator.Referring to FIG. 16C, external film 1205 may have dimpled regions 1213on a single surface of the external film that act as concave lenses.Referring to FIG. 16D, the external film 1205 may have Fresnel lenses inthe regions 1214. In other embodiments, holographic or diffractiveoptical elements may be disposed at the regions 1214. These opticalelements may scatter or diffract light and may operate as lenses, forexample, with negative power that redirect light incident on the lensestoward the active regions. Referring to FIG. 16E, external film 1205 mayhave opposing sloped surfaces 1215 to refract light in oppositedirections toward different active regions. FIG. 16F shows the externalfilm 1205 having surfaces 1215 oriented similarly so as to refract lightin the same direction. Referring to FIG. 16G, external film 1205 mayhave one or more reflecting sloped surfaces 1216 that reflect lighttoward active regions. Many other configurations are possible that alsoaccomplish the desired redirection of light at the external film 1205.

Referring now to FIG. 17, an interferometric modulator 1200 can includean external film 1205 that is connected to the outer surface of thespatial light modulator 105, where the film 1205 is configured tocollect light incident at a wide range of angles and direct the lightinto at a narrower range of angles onto the light-modulating elements.In FIG. 17, the external film 1205 is configured to receive incidentlight 1206, 1207 at various angles and substantially collimate the light(represented by arrows 1208, 1209) and direct the light towards theactive reflectors 1211. In some embodiments, such as the one shown inFIG. 17, the external film 1205 includes collimating elements 1218 thatsubstantially collimate the light. In some embodiments, the externalfilm 1205 includes a plurality non-imaging optical elements, e.g.,compound parabolic collectors, 1218. The non-imaging optical elements,e.g., compound parabolic collectors 1218, collimate at least some of thelight 1206 and 1207 that is incident on the external film 1205 at arange of angles. A portion of the light 1208 and 1209 then exits thecompound parabolic collectors 1218 at a more normal angle and isdirected towards the active reflectors 1211. Some of that light 1208 and1209 is then reflected by the active reflectors 1211 and exits thedisplay 1200 as light 1210 a and 1210 b egressing from the display 1200at a limited range of angles. Accordingly, the film 1205 has a limitedfield-of-view. In some embodiments, at least some of the light 1210 aand 1210 b exits the display 1200 at a cone angle not greater than about70 degrees from a plane 610 normal to a front surface of the externalfilm 1205. In some embodiments, the cone angle is no more than about 65,60, 55, 50, 45, 40, 35, 30, 25, or 20 degrees from the plane 610 normalto the front surface of the external film 1205. The collimating elements1205 effectively limit the field-of-view of the device 1200 becauselight generally does not egress from the display 1200 at an anglesubstantially greater than the incident angle. Accordingly, thefield-of-view of the external film may be about 70, 65, 60, 55, 50, 45,40, 35, 30, 25, or 20 degrees or less as measured from the normal. Theseangles are half-angles. Other values outside these ranges are alsopossible.

FIGS. 18A-C depicts another embodiment of a display 1300 that includesan optical film 1305 disposed forward of the spatial light modulator105. The optical film 1305 is configured to receive light incident at awide range of angles and direct the light into a narrower range ofangles onto the light-modulating elements. The optical film 1305 alsodiffuses light. In certain embodiments, the optical film 1305 isconfigured to diffuse light such that light incident on the diffuserelement is directed to the light-modulating elements more collimatedthan the incident light.

In one embodiment, the optical film 1305 comprises a holographicdiffuser. The holographic diffuser comprises diffractive featuresarranged to manipulate the light, for example, to produce a heightenedintensity distribution over a narrow range of angles. In anotherembodiment, the optical film 1305 includes a plurality of non-imagingoptical elements, e.g., a plurality of compound parabolic collectorssuch as described above and a thin layer of diffusing material on anupper surface 1340 of the optical film 1305. In another embodiment, theoptical film 1305 includes other collimating elements with a film ofdiffusing material on the outer surface 1340.

Referring to FIG. 18A, the film 1305 is configured to receive incidentlight 1310. Referring to FIG. 18B, the film is also configured tosubstantially redirect the incident light 1310 (the substantiallyredirected light being represented by arrows 1315), which is directed toactive reflectors within the spatial light modulator 105, toward thenormal to the surface of the active reflectors. For incident light overthe range of +/−75 degrees the redirected light can be in the range of+/−35 degrees, wherein the angles are measured from the normal. In thisembodiment, the redirected light is substantially collimated. In someembodiments, the reflectors may be at a bottom portion of the spatiallight modulator 105. Referring to FIG. 18C, the light 1325 reflectedfrom the active reflectors enters the lower surface 1330 of film 1305.The film 1305 is configured to receive the reflected specular light atits lower surface 1330 and is diffused before it is emitted from thefilm 1305 as diffuse light. In some embodiments, the light is diffusedas it propagates through the film 1305. In other embodiments, the lightis diffused at the upper surface 1340 (or lower surface 1330) of thefilm 1305. Other configurations or values outside the ranges above arealso possible.

The foregoing description details certain embodiments of the invention.It will be appreciated, however, that no matter how detailed theforegoing appears in text, the invention can be practiced in many ways.As is also stated above, it should be noted that the use of particularterminology when describing certain features or aspects of the inventionshould not be taken to imply that the terminology is being re-definedherein to be restricted to including any specific characteristics of thefeatures or aspects of the invention with which that terminology isassociated.

1. A display comprising: a substrate; a light-modulating arraycomprising a plurality of light-modulating elements, saidlight-modulating array comprising a plurality of active regions andnon-active regions; and a plurality of light redirecting elementsdisposed on a side of the light-modulating elements such that theplurality of light redirecting elements are concentrated above thenon-active regions of the light-modulating array in comparison to theactive regions of the light-modulating array, wherein the lightredirecting elements are configured to re-direct light propagating fromabove the light redirecting elements and the substrate and incident onthe redirecting elements into the active regions of the light-modulatingarray, wherein the active regions are spaced apart from each other, andwherein the display is a reflective display.
 2. The display of claim 1,wherein the redirecting elements are disposed between thelight-modulating elements and the substrate.
 3. The display of claim 1,wherein the substrate is disposed between the redirecting elements andthe light-modulating elements.
 4. The display of claim 1, wherein saidredirecting elements comprise reflecting surfaces.
 5. The display ofclaim 1, wherein said redirecting elements comprise scatter elementsthat scatter light incident thereon.
 6. The display of claim 1, whereinsaid redirecting elements comprise lenses.
 7. The display of claim 6,wherein said lenses have negative power.
 8. The display of claim 7,wherein said lenses comprise concave surfaces that form concave lenses.9. The display of claim 6, wherein said lenses comprise Fresnel lenses.10. The display of claim 1, wherein said redirecting elements comprisediffractive optical elements.
 11. The display of claim 1, wherein saidredirecting elements comprise holographic regions.
 12. The display ofclaim 1, wherein said redirecting elements comprise sloped surfaces. 13.The display of claim 1, wherein said redirecting elements compriseopposing sloped surfaces.
 14. The display of claim 1, wherein saidredirecting elements comprise total internal reflection elements. 15.The display of claim 1, wherein said redirecting elements have widthsbetween about 2 and 10 microns.
 16. The display of claim 1, wherein saidredirecting elements are spaced apart by a distance of between about 125and 254 microns.
 17. The display of claim 1, further comprising: aprocessor that is in electrical communication with the light-modulatingarray, said processor being configured to process image data; and amemory device in electrical communication with said processor.
 18. Thedisplay of claim 17, further comprising: a first controller configuredto send at least one signal to the light-modulating array; and a secondcontroller configured to send at least a portion of said image data tosaid first controller.
 19. The display of claim 17, further comprising:an image source module configured to send said image data to saidprocessor.
 20. The display of claim 19, wherein said image source modulecomprises at least one of a receiver, transceiver, and transmitter. 21.The display of claim 17, further comprising: an input device configuredto receive input data and to communicate said input data to saidprocessor.
 22. The display of claim 1, wherein said light-modulatingelements comprise spatial light modulators configured to form an image.23. The display of claim 1, wherein said light-modulating elementscomprise movable reflective surfaces, static reflective surfaces, andoptical resonant cavities between the movable reflective surfaces andthe static reflective surfaces.
 24. The display of claim 23, wherein theactive regions include the optical resonant cavities.
 25. The display ofclaim 1, wherein said light-modulating elements compriseelectromechanical mirrors.
 26. The display of claim 1, wherein saidlight-modulating elements comprise interferometric light modulators. 27.The display of claim 1, wherein the non-active regions include spacesbetween adjacent said active regions.
 28. A display comprising: meansfor modulating light, the light-modulating means including a pluralityof active regions and non-active regions, the active regions spacedapart from each other; means for supporting the light-modulating means;and means for redirecting light propagating from above thelight-redirecting means and the supporting means and incident on thelight-redirecting means into the active regions of the light-modulatingmeans, the light-redirecting means disposed on a side of thelight-modulating means such that the light-redirecting means areconcentrated above the non-active regions of the light-modulating meansin comparison to the active regions of the light-modulating means,wherein the display is a reflective display.
 29. The display of claim28, wherein the supporting means includes a substrate.
 30. The displayof claim 28, wherein the light-modulating means includes a plurality oflight-modulating elements.
 31. The display of claim 28, wherein thelight-redirecting means includes a plurality of light-redirectingelements.
 32. A method of manufacturing a display, the methodcomprising: disposing a plurality of light redirecting elements on aside of a light-modulating array on a substrate, the light-modulatingarray including a plurality of light-modulating elements, thelight-modulating array including a plurality of active regions andnon-active regions, the active regions spaced apart from each other,wherein the plurality of light redirecting elements are concentratedabove the non-active regions of the light-modulating array, wherein thelight redirecting elements are configured to re-direct light propagatingfrom above the light redirecting elements and the substrate and incidenton the redirecting elements into the active regions of thelight-modulating array, and wherein the display is a reflective display.33. A reflective display manufactured by the method of claim 32.